1. Field of the Invention
The present invention relates to a semiconductor device chip wafer testing method and apparatus for detecting a crystal defect in a wafer stage during a process for manufacturing a semiconductor device, in particular, a compound semiconductor laser diode or a light emitting diode.
2. Related Background Art
In a general method of manufacturing a compound semiconductor laser diode device, plural kinds of compound semiconductor layers are successively formed through crystal growth on a predetermined substrate and stacked to manufacture an epitaxial wafer. Next, in order to obtain a stripe structure serving as a resonator, the wafer is etched to remove a part thereof. After a film formation process including impurity diffusion, crystal growth, and electrode formation is completed, the wafer is cleaved and diced into individual chips (chip dicing).
There has been known that a crystal defect called “dislocation” occurs in the above-mentioned process for manufacturing the wafer for the compound semiconductor laser diode device. In general, a compound semiconductor substrate includes a crystal defect. Therefore, when epitaxial growth is made on the compound semiconductor substrate, the defect grows in a stacked compound semiconductor layer. Even at a position in which the crystal defect does not exist on a surface of the substrate, a new crystal defect is caused due to an impurity or the like which is deposited on the surface of a layer of compound semiconductor layers successively stacked during a crystal growth process and then grows. When the crystal defect exists in a stripe structural portion, a dark line defect (DLD) grows from a crystal defect portion by energization during operation. Therefore, light power reduces and the life of the compound semiconductor laser diode device shortens, so that the reliability of the device significantly reduces.
Thus, according to a conventional technique, a testing method of discriminating a deteriorated product having a short life through aging which means that a completed product of the compound semiconductor laser diode device is operated for several hours to several tens of hours under a high-temperature environment is generally used in order to remove a defect element in which a crystal defect exists in the stripe structural portion. However, such an aging method causes an increase in manufacturing cost of the laser diode device. In addition, it is hard to detect all products having the crystal defect using only the aging method.